The long-term effectiveness of vein bypass grafts is limited by the development of neointimal hyperplasia and accelerated atherosclerosis. Using a rabbit model, we have shown that a bioengineering strategy that inhibits cell cycle regulatory gene expression with antisense oligonucleotides creates vein grafts that are resistant to neointima formation and accelerated atherosclerosis in hyperlipidemic animals. The goal of this project is to elucidate the mechanistic basis of this anti- atherogenic property. It is postulated that atherogenesis is related to an imbalance between th generation of nitric oxide (NO) and reactive oxygen species. Our preliminary data indicate that the atherosclerosis-prone control grafts are dysfunctional as evidenced by impaired endothelium-dependent vasorelaxation, decreased NO bioactivity, increased superoxide anion generation, increased VCAM-1 expression and a highly adhesive endothelium. In contrast, the genetically engineered grafts retain relatively normal function. This project will test the hypothesis that the preservation of NO bioactivity and the resulting inhibition of oxidative stress confers the long-term anti-atherogenic property of the bioengineered grafts. The creation of genetically engineered vein grafts provides us with a novel experimental model system for defining the critical pathobiologic processes of lesion formation in vein grafts. We will employ an in vivo gene transfer experimental approach to s electively augment the expression of given molecule as a direct means of defining the causal role of putative mediators of vascular lesion formation. Specifically, we will test the hypothesis that the preservation of normal NO activity within the bioengineered graft exerts a chronic inhibitory effect on vein graft atheroma formation by: 1) reducing the oxidative stress induced by increased superoxide anion generation, 2) down-regulating the expression of adhesion molecules such as VCAM-1 and 3) inhibiting the endothelial- monocyte interactions necessary for atheroma formation. These studies will have provide new insights into molecular basis of vein graft lesion formation and further define the clinical utility of this bioengineering approach in the treatment of human vascular disease.